Points to GN250 Electronic Ignition Conversion

[Jim]

Jack, aka @Team Junk started a thread on using the $20 Suzuki Gn250 igniter box as a replacement for the unobtanium TCI box for our 80 and up bikes. Jack's the genius behind this. He spent the better part of 2 yrs researching iggy boxes to find one that had a built in advance that will work for our motors. My 80SG was the first bike to run with the GN box. So I can confirm that it does indeed work. I'll put up a link to that thread, but last I checked it's over 20-30 pages long. Here's the link. Rather than bury this points conversion in the back of that thread, I'm starting this one. I'm the one designing the conversion, so it only makes sense for me to have control over my own thread.

Since I don't have a running points bike, I built a test stand. This will make modding it much easier and I don't have to keep my SG out of service while doing the mod. I'm a little gimped up at the moment, so don't expect this to happen overnight.... sometime in late summer, early fall should be doable. When it's done this should be an easy peasy, detailed, step by step how-to for anyone with enough skill to keep an XS running. I'll reserve some comments below this one to keep everything nice and tidy and I'll leave a comment at the end everytime I add something to them. So.... without further ado.... here's Juju, the test stand.

 

[Jim]

What we're doing here is develop a low cost alternative electronic ignition system for the 70 to 79 XS650. While I’m sure this could be adapted to other engines, our focus will be the XS.

Goals:
Crankshaft Triggered. All modern engines employ a crank triggered system because it’s inherently more accurate and stable than a cam triggered system.

Low Cost. Under $50 is the target. The Suzuki GN250 box can be had for about $20. The trigger coil comes in under $10. Other misc parts will bring us close to out mark.

Built in Electronic Advance. No moving parts means maintenance free.

DIY. Design a conversion that’s easily done by your average backyard wrench using nothing more than hand tools and a drill press.

Step By Step. Instructions laid out in a logical, easy to follow sequence.

No Loss in Performance.




cont.

 

[Jim]

Mechanical Modifications.
Stator.

 

[Jim]

Mechanical Modifications.
Rotor.

So... I'm gonna run through the magnet installation, but first... here's a shot of the finished rotor next to an OEM TCI rotor. You can see the line I drew that runs from the edge of the timing mark to the edge of the magnet and then a line from the center of the magnet to the center of the rotor. With the ruler butted up against the shoulder of the mount tower, everything lines up. Duplicate this on the rotor you're converting. Measure in from the edge .175" and make a mark. This is the center point for the hole.

Used a 1/4" end mill in a drill press. Went slightly over 1/16" deep.

Installed the magnet with JB Weld.

I never tested the rotor with the 4 existing ferrous screws installed out at the edge of the rotor, so I don't know if they'll interfere with the pickup. I replaced them with non-magnetic stainless screws (3 X 0.5mm X 8mm long). I also modded one using brass screws. If you try it without replacing the existing screws, please leave a comment and let up know how it did.

 

[Jim]

Mechanical Modifications.
Crankshaft Position Sensor (Pickup).
Standby

 

[Jim]

Electrical Modifications.
Standby

 

[TwoManyXS1Bs]

Nice test stand, Jim.

Maybe add a timing light, affixed and aimed at the timing marks?




.......or a turn coordinator...

 

[Jim]

Nice test stand, Jim.

Maybe add a timing light, affixed and aimed at the timing marks?

.......or a turn coordinator...

Turn coordinator's on backorder..... 'sides... I can still do a 2 min turn in my sleep.
Timing light it is...

 

[2XSive]

What a great project that will serve as a superior upgrade compared to any cam driven ignition system, at a fraction of the cost. Way to go Jim.

 

[halfmile]

Just out of curiosity is that motor one that I sold you last fall?? Nice test stand by the way.

 

[Jim]

Just out of curiosity is that motor one that I sold you last fall?? Nice test stand by the way.

Yeah.... came out of one of those 3 bikes. Bet you didn't know it ran?
.... and no.... we ain't renegotiating the price.

 

[halfmile]

Yeah the guy I got them from said he had one of them running but who would ever believe anything you hear when buying a motorcycle.. Glad that worked out for you.

 

[MacMcMacmac]

I think the GN mod is a no brainer. Between a stock tci, a backup points system, a GN box, and solid state rectifier you could have a bike ready for the zombie apocalypse. If only the stock rotor could be fixed once and for all.

 

[jetmechmarty]

If only the stock rotor could be fixed once and for all.

Say it ain't so, Mac! My bike is temporarily out of commission due to too many distractions, but my rewound rotor has 15 years on it. I haven't been reading about failed rewinds. I'm feeling like I missed something.

 

[Jim]

Say it ain't so, Mac! My bike is temporarily out of commission due to too many distractions, but my rewound rotor has 15 years on it. I haven't been reading about failed rewinds. I'm feeling like I missed something.

Granted it's only just over a year since I started rewinding.... but 50+ now with no fails.
I suspect mine will last at least as long as the original.

 

[jetmechmarty]

Granted it's only just over a year since I started rewinding.... but 50+ now with no fails.
I suspect mine will last at least as long as the original.

Depending upon your wire insulation, but yes, I be surprised if I ever had to replace a rotor again. Custom Rewind in Alabama has been doing these for many years and I have never heard or seen a complaint. Wire insulation is better now than it was when these bikes were built.

Years ago, I was on the midnight shift maintaining 1970s vintage airplanes. We'd find short circuits by manipulating the wires in the dark. The short circuits would light up at breaks in the insulation. Maybe that's why the avionics troubleshooters were called spark chasers. The days of doing that are all but gone. The wire is better now.

 

[Superjet]

Delete

 

[MacMcMacmac]

Say it ain't so, Mac! My bike is temporarily out of commission due to too many distractions, but my rewound rotor has 15 years on it. I haven't been reading about failed rewinds. I'm feeling like I missed something.

Sorry Marty, still have PTSD over mine from a couple of years ago... .

 

[MaxPete]

Hi Jim / All: I have been away (family health stuff, daughter #3 house purchase and....a couple of other things....) and am just catching up.

This is an excellent initiative and as MacMcMacmac said above, this will really settle one of the few challenges to running the XS650 into the next century.

I cannot think of anyone who will accomplish it more effectively and efficiently than Jim.

This one truly rates:

Pete

 

[Signal]

Thank you Jim.